1. Field of the Invention
The present invention relates to a method and related communication device in a wireless communication system, and more particularly, to a method and related communication device of the wireless communication system for handling a procedure parameter change.
2. Description of the Prior Art
General Packet Radio Service (GPRS) is a service in a GSM (Global System for Mobile communications) system, and is one of the objects of the standardization work at ETSI (European Telecommunication Standard Institute) and 3GPP (Third Generation Partnership Project).
In the GPRS operational environment, serving GPRS support nodes (SGSN), each of which is connected to the GSM mobile communication network including a base station subsystem (BSS), can provide a packet service for mobile data terminals via several base stations (BS), i.e. cells. The BSS is a radio interface providing functionalities to provide radio access to a MS (Mobile Station). A BSS serves a subset of cells that constitute a Routing Area (RA).
Mobility Management (MM) in GPRS system supports GPRS Attach, GPRS Detach, authentication, routing update, location update, activation of a PDP context, and deactivation of a PDP context. For mobility management, logical routing areas have been defined to the GPRS network. A routing area RA is an area defined by an operator, comprising one or more cells. Usually, one SGSN serves several routing areas. A routing area is used for determining the location of the MS in the standby state. If the location of the MS is not known in terms of a specific cell, signalling is started with a GPRS page within one routing area RA.
A routing area updating procedure is used for supporting mobility management of a packet switched domain. A routing area (RA) updating procedure takes place when a GPRS-attached MS detects that it has entered a new RA, when a periodic RA update timer has expired, or when the MS has to indicate new access capabilities to the network or, for A/Gb mode, when a suspended MS is not resumed by the BSS (Base station subsystem).
A combined RA/LA (location Area) updating procedure takes place when the MS enters a new RA or when a GPRS-attached MS performs an IMSI attach or when the MS has to indicate new access capabilities to the network, or when a suspended MS is not resumed by the BSS. The MS using GPRS in MS operation mode A performs the normal routing area update procedure during an ongoing circuit-switched transaction.
In the abovementioned two RA updating procedure, procedure message exchange between the MS and the SGSN are described as follows. A ROUTING AREA UPDATING REQUEST message is sent from the MS to the SGSN. In response, a ROUTING AREA UPDATING ACCEPT message is sent from the SGSN to the MS. As last, a ROUTING AREA UPDATING COMPLETE message is sent from the MS to the SGSN, indicating that the procedure is completed.
The ROUTING AREA UPDATING ACCEPT message can include a P-TMSI (Packet-Temporary Mobile Subscriber Identity), an RAI (Routing Area Identifier) and includes a GMM (GPRS Mobility Management) cause for indicating the procedure failure, such as ‘MSC temporarily not reachable’, ‘network failure’, or ‘Congestion’.
A P-TMSI is a temporary identity issued to a GPRS enabled mobile and unique within a given RA and is used by the GPRS network to page the specified mobile. The P-TMSI has 32 bits and is associated with the TLLI (Temporary Logical Link Identifier). When a new P-TMSI is assigned by the network, the MS and the network shall handle the old and the new P-TMSI as follows.
Upon receipt of a GMM message (e.g. Routing Area Updating Accept) containing a new P-TMSI, the MS considers the new P-TMSI and new RAI and also the old P-TMSI and old RAI as valid in order to react to paging requests and downlink transmission of LLC (Logic Link Control) frames. For uplink transmission of LLC frames the new P-TMSI shall be used. The MS shall consider the old P-TMSI and old RAI as invalid as soon as an LLC frame is received with the local TLLI (Temporary Logical Link Identity) derived from the new P-TMSI.
Upon the transmission of a GMM message containing a new P-TMSI, the network shall consider the new P-TMSI and new RAI and also the old P-TMSI and old RAI as valid in order to be able to receive LLC frames from the MS. The network shall consider the old P-TMSI and old RAI as invalid as soon as an LLC frame is received with the local TLLI derived from the new P-TMSI.
A GPRS suspension procedure enables the network to suspend GPRS services packet flow in the downlink direction. The GPRS suspension procedure shall be used to suspend GPRS services:                a) when the mobile station in a class A mode of operation is handed over to a cell where the support of Class A mode of operation is not possible (e.g. a DTM mobile station entering a cell not supporting DTM);        b) when the GPRS attached mobile station is in a cell that does not support DTM and a circuit switched service is initiated.        
The GPRS suspension procedure is initiated by the MS by sending a GPRS SUSPENSION REQUEST message including a suspension cause, a TLLI, and an RAI to a BSC (Base Station Controller). The BSC transfers the GPRS SUSPENSION REQUEST message with the TLLI and RAI to the SGSN. The SGSN acknowledges by returning a GPRS SUSPENSION ACK or rejects by returning a GPRS SUSPENSION NACK. The TLLI is derived from the in use P-TMSI of the MS.
When the SGSN assigns a new P-TMSI to the MS through the routing area updating procedure, the ROUTING AREA UPDATING ACCEPT message includes the new P-TMSI. The MS starts to use the new P-TMSI after receiving the ROUTING AREA UPDATING ACCEPT message. Finally, the MS needs to respond with the ROUTING AREA UPDATING COMPLETE message, and thereby the SGSN confirms the P-TMSI change.
If a circuit switched initiation, such as a MO (Mobile Originating) call, occurs before transmission of the ROUTING AREA UPDATING COMPLETE message and after transmission of the ROUTING AREA UPDATING ACCEPT message, the ROUTING AREA UPDATING COMPLETE message is skipped or blocked, indicating that the P-TMSI change is not confirmed by the SGSN.
For a MS using GPRS services, the circuit switched initiation requires the MS to perform GPRS suspension procedure. In a situation where a new P-TMSI is assigned and the ROUTING AREA UPDATING COMPLETE message is skipped, the MS still initiates the GPRS suspension procedure with a TLLI derived from the new P-TMSI. However, the SGSN rejects the GPRS suspension request since the P-TMSI change is not confirmed by the network. Consequently, the GPRS suspension procedure is failed, and the SGSN pages the MS if there is data sent to the MS. This wastes radio resource for paging since the MS cannot receive this paging in the dedicated mode which the MS enters after the GPRS suspension procedure is performed.